The present invention relates to a method for the synthesis of 2-(4-amidophenoxy)alkanoic acids and esters and 2-(4-aminophenoxy)alkanoic acids and esters. Such compounds are useful in the production of pharmaceuticals and herbicides. See, for example, U.S. Pat. Nos. 3,278,524; 3,081,302; 4,439,226, 4,358,307 and British Pat. No. 916,242.
U.S. Pat. No. 3,278,524, teaches the preparation of 2-(4-acetaminophenoxy)propanoic acid by reacting 2-halo propionic acids with 4-acetaminophenol under basic conditions. Similarly, U.S. Pat. No. 3,081,302, teaches the condensation of 4-acetaminophenol with 2-halo-alkanoic acid esters in the presence of a base to give 2-(4-acetaminophenoxy)alkanoic acid esters. Such a process is economically disadvantageous, and hence the poor yield.
U.S. Pat. No. 4,439,226, and Journal of Organic Chemistry (Vol.36, pages 1171-1178, 1971) describe the synthesis of 2-(4-aminophenoxy)propanoic acid esters via sequential condensation of 4-nitrophenol with 2-halopropanoic acid esters in the presence of a base and reduction. These processes proceeds with moderate yields and hence they are not economically advantageous. Furthermore, salts of nitrophenols can explode if allowed to become dry, especially if heated.
The prior art does not disclose the conversion of acylaromatic compounds to the corresponding acetamide or aminoaromatic compounds. Such a process would be economically desired as it overcomes the deficiencies mentioned heretofore.
The present invention provides a procedure for producing intermediates which are 2-(4-aminophenoxy)alkanoic acids or esters, preferably, 2-(4-acetaminophenoxy)alkanoic acids or esters as well as 2-(4-aminophenoxy)alkanoic acids or esters.